CVE-2026-40873
Quarantine item: unescaped attachment filenames enable JavaScript in admin UI.
Is CVE-2026-40873 being exploited?
Not confirmed. CVE-2026-40873 does not appear in CISA's Known Exploited Vulnerabilities catalog, which records only exploitation that has been observed and reported publicly. That is evidence of absence of a report, not evidence the flaw is unattacked. EPSS currently estimates a 0.33% probability of exploitation in the next 30 days.
How severe is CVE-2026-40873?
CVE-2026-40873 is rated High with a CVSS score of 8.9. Severity describes how bad exploitation would be, not how likely it is: pair it with exploitation evidence before deciding what to patch first.
Is there a patch for CVE-2026-40873?
Yes. A fix has been recorded for CVE-2026-40873. The vendor advisory is the authority on the exact fixed version — apply it from there rather than from a summary.
What does CVE-2026-40873 affect?
CVE-2026-40873 affects mailcow: dockerized, Quarantine details modal in mailcow. Confirm the exact affected versions against the vendor advisory before deciding you are exposed.
What should I do about CVE-2026-40873?
Upgrade to 2026-03b release; apply patch; validate rendering.
Exploitation status reflects CISA's KEV catalog as we last synced it. Check the catalog directly.
Attacker can execute JS in the admin's browser when viewing quarantine, potentially hijacking the admin account.
Patch when possible
- affected< 2026-03b
As published in the CVE Program record. A version outside these ranges is not a statement that it is unaffected — vendors sometimes understate a range, and distribution-backported builds carry upstream numbers that do not reflect what was patched into them.